With regard to a vehicle, in recent years, a hybrid vehicle as an electrically powered vehicle is proposed and put into practical use for the purpose of improvement of fuel efficiency. The hybrid vehicle is classified into a series type hybrid vehicle which exists as a means for generating electric energy by an internal combustion engine to make a power generator (motor) drive a vehicle by the electric power, and a parallel type hybrid vehicle which rotates a driving wheel by an internal combustion engine and a power generator.
In the series type hybrid vehicle, since the internal combustion engine is not coupled to a driving wheel, traveling in a region where a combustion efficiency of the internal combustion engine is high is possible.
A control device for an electric vehicle engine driven generator according to Patent Literature 1 controls an air-fuel ratio of an internal combustion engine in correspondence with a generated power fluctuation obtained based on a detected generated power, in order that an average generated power comes closer to a lean limit when the average generated power is near a predetermined target value.
A hybrid vehicle according to Patent Literature 2 which detects a torque fluctuation and performs air-fuel ratio control controls an air-fuel ratio of an internal combustion engine based on a fluctuation amount of a generated power of a power generator in a quasi normal operation state where a fluctuation of an operating condition of the internal combustion engine is equal to or less than a predetermined amount.